Systems that control functions such as gain control of amplifiers or current control through a device often include a closed loop control system such that a suitable circuit receives a target value and automatically controls a target circuit such that it exhibits an appropriate response, such as gain or current flow.
In some systems, fine control is desirable. This generally involves the use of a digital to analog converter having a relatively small step size between adjacent steps. Some systems may have relatively large and variable offset voltages. This tends to involve a digital to analog converter having a sufficiently large output range. If fine control and a large offset occur in a single system, this tends to involve the use of a high resolution digital to analog converter, with associated cost issues in fabricating such a large (e.g., large number of input bits in its input word) precision device. Cost rises because such a device has a bigger footprint on an integrated circuit die. It would be desirable to achieve fine control without having to fabricate high resolution and wide range analog to digital converters.